Passive surveillance is collecting notifications of adverse events (AE) on the whole population but the sensitivity of this system is not high and its timeliness is not necessarily optimal. Last year, with the new pandemic Influenza vaccine the investigators piloted a web-based active surveillance of a large number of health care workers (HCW) vaccinated with the new adjuvanted monovalent pH1N1 influenza vaccine (Arepanrix® GSK, Canada). Because healthcare workers (HCW) constituted a well-defined group with general good health and received the Influenza vaccine in priority, this group of people was well suited for monitoring the safety of the influenza vaccine. For this study, 6242 HCW were recruited in three different sites (5183 were from Quebec). A total of 468 events (local reactions, fever, systemic reactions, gastrointestinal and respiratory problems) were reported by 430 HCW. 80% of the HCW recruited completed at least one of the three surveys and 52% responded to all questionnaires. During this surveillance, the investigators didn't have unexpected findings but this active surveillance of adverse events among healthcare workers would have been effective enough to rapidly detect adverse events occurring at a rate ≥ 1 per 200 vaccinees. For this year the investigators want to expand the surveillance to more sites and more participants to be able to detect AE occurring at rates ≥ 1 per 500 vaccinees, and to increase the response rate to all three surveys in participants.